From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759768AbZE0FTo (ORCPT ); Wed, 27 May 2009 01:19:44 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758658AbZE0FTa (ORCPT ); Wed, 27 May 2009 01:19:30 -0400 Received: from cn.fujitsu.com ([222.73.24.84]:61235 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1755763AbZE0FTa (ORCPT ); Wed, 27 May 2009 01:19:30 -0400 Message-ID: <4A1CCD84.2040607@cn.fujitsu.com> Date: Wed, 27 May 2009 13:20:04 +0800 From: Xiao Guangrong User-Agent: Thunderbird 2.0.0.6 (Windows/20070728) MIME-Version: 1.0 To: Thomas Gleixner CC: mingo@elte.hu, Mathieu Desnoyers , LKML , Zhaolei , kosaki.motohiro@jp.fujitsu.com, Steven Rostedt , fweisbec@gmail.com Subject: Re: [PATCH 0/3] ftrace: add tracepoint for timer event References: <4A1673AF.30508@cn.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Thomas Gleixner wrote: > On Fri, 22 May 2009, Xiao Guangrong wrote: >> We already have debugobject in timer to init/activate/deactivate/free, >> but it can't be covered function of there tracepoints, because: >> 1: We can't get timer's lifecycle information in userspace by debugobject, >> it is necessary for system engineer to investigate system trouble caused >> by using timer. >> 2: We can't get information of whole lifecycle of timer by debugobject, >> for example, deactivation of a timer. >> 3: There are many different tracing code in many kernel subsystem as >> blktrace, debugobject, and tracepoint is designed as generic way >> to unify these tracing way. > > No. You can not unify debugobject into tracepoints. debugobjects is a > totally different beast. It's main purpose is to prevent undebugable > system crashes which we have seen several times e.g: freeing of an > active timer, reinitializing of an active timer ... > > Dealing with these problems is not covered by tracepoints by any > means. The trace point does not prevent the system crash which happens > 2 seconds after the fact that an active timer is kfree'd, debugobject > does and it points you to the exact place where the shit happens. > > I'm not opposed to add tracepoints to the timer code at all. In fact I > appreciate that, but your idea of substituting debugobjects with > tracing is just plain wrong. > > It's the other way round. tracing can reuse the existing debugobject > hooks to insert trace points, but it can not replace the functionality > at all. > Hello tglx: Thanks for you review! Totally agree. Actually I do know the difference between debugobject and tracepoint. Sorry for making you misunderstand what I said for my pool English. Thanks, Xiao Guangrong > tglx > >